On Wed, Jan 13, 2016 at 9:30 PM, Takashi Iwai <tiwai@xxxxxxx> wrote: > On Wed, 13 Jan 2016 20:41:30 +0100, > Dmitry Vyukov wrote: >> >> On Wed, Jan 13, 2016 at 8:30 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: >> > On Wed, Jan 13, 2016 at 8:05 PM, Takashi Iwai <tiwai@xxxxxxx> wrote: >> >> On Wed, 13 Jan 2016 19:34:36 +0100, >> >> Dmitry Vyukov wrote: >> >>> >> >>> On Wed, Jan 13, 2016 at 5:53 PM, Takashi Iwai <tiwai@xxxxxxx> wrote: >> >>> > This and your other relevant reports seem pointing the race of timer >> >>> > ioctls. Although snd_timer_close() itself calls snd_timer_stop(), >> >>> > there is no other protection against the concurrent execution. >> >>> > >> >>> > If my guess is correct, a simplistic fix like below should work. It >> >>> > basically serializes the timer ioctl by using a new mutex (and >> >>> > replacing the old tread_sem mutex). They are no longtime blocking >> >>> > calls, so this shouldn't be a big problem. But certainly there can be >> >>> > a less intrusive way to paper over this if this really matters. >> >>> > >> >>> > In this case for timer.c, I'd leave the final decision rather to >> >>> > Jaroslav. Jaroslav, what do you think? >> >>> >> >>> >> >>> After applying this patch I still see the following WARNINGS: >> >>> >> >>> ------------[ cut here ]------------ >> >>> WARNING: CPU: 2 PID: 30398 at lib/list_debug.c:53 __list_del_entry+0x10b/0x1e0() >> >>> list_del corruption, ffff880032d933b0->next is LIST_POISON1 (dead000000000100) >> >>> Modules linked in: >> >>> CPU: 2 PID: 30398 Comm: syz-executor Not tainted 4.4.0+ #241 >> >>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 >> >>> 00000000ffffffff ffff8800627778d8 ffffffff82926eed ffff880062777948 >> >>> ffff880061c2af80 ffffffff8660b640 ffff880062777918 ffffffff81350c89 >> >>> ffffffff8298e77b ffffed000c4eef25 ffffffff8660b640 0000000000000035 >> >>> Call Trace: >> >>> [< inline >] __dump_stack lib/dump_stack.c:15 >> >>> [<ffffffff82926eed>] dump_stack+0x6f/0xa2 lib/dump_stack.c:50 >> >>> [<ffffffff81350c89>] warn_slowpath_common+0xd9/0x140 kernel/panic.c:483 >> >>> [<ffffffff81350d99>] warn_slowpath_fmt+0xa9/0xd0 kernel/panic.c:495 >> >>> [<ffffffff8298e77b>] __list_del_entry+0x10b/0x1e0 lib/list_debug.c:51 >> >>> [< inline >] list_del_init include/linux/list.h:145 >> >>> [<ffffffff84ebd199>] _snd_timer_stop+0x119/0x450 sound/core/timer.c:501 >> >> >> >> This is >> >> >> >> list_del_init(&timeri->active_list); >> >> >> >> right? Possibly the following oneliner covers it? >> > >> > Yes, that is this line. >> > Yes, these two patches fix use-after-frees and GPFs. >> > >> > Tested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> >> >> >> I've re-tested the programs that I reported. But when I started the >> fuzzer again I hit a similar use-after-free in snd_timer_interrupt: > > Is it the result with all patches, i.e. four patches (two for > sequencer and two for timer)? Yes, with 4 recent patches. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
